The present invention relates to an ultrasonic transmitting-receiving apparatus in which ultrasonic echo signals from other transmitting apparatus are eliminated.
In the prior ultrasonic transmitting-receiving apparatus, when a first Liming pulse is transmitted from a timing pulse generating means to an oscillator, a first pulse signal from the oscillator is supplied to an ultrasonic vibrator, a first pulse-like ultrasonic signal is emitted from the ultrasonic vibrator to water, and first pulse signal and first echo signals from an object and the bottom of the sea are successively displayed on a display device. Also, when the next timing pulse is transmitted from the timing pulse generating means to the oscillator, the next transmitting signal and the next echo signals from an object and the bottom of the sea are received through the ultrasonic vibrator by a receiving device. Then, when common signals are selected between the first signals and next signals, even if interference signals are comprised of the first or second signals, the interference signals are removed from the selected signals and the necessary signals are displayed on the display device.
In such ultrasonic transmitting-receiving apparatus, when an object in the water is contacted by ultrasonic wave from the first ultrasonic vibrator and the same object is contacted by ultrasonic signals from the second ultrasonic vibrator having the same timing interval close to the timing interval of the first ultrasonic vibrator, the echo signals due to the ultrasonic wave from the first ultrasonic vibrator and the interference signals from the second ultrasonic vibrator are displayed on the display device.
Therefore, because the necessary signals and the interference signals are supplied to the receiving device of the same timing, when the common signals between the first signals and the second signals are selected, the interference signals cannot be eliminated.